A closed loop solar energy collecting system has been described in my U.S. Pat. No. 4,286,579, issued Sept. 1, 1981.
The system includes a concentrating reflector, vaporizer means at the focal point of the reflector, a fluid metering assembly attached to the input end of the vaporizer means for precisely metering a quantity of a vaporizable heat transfer fluid from a supply tank to the vaporizer means, a heat exchanger, and a fluid storage reservoir. Solar energy concentrated by the reflector on the vaporizer means vaporizes the heat transfer fluid. The heated vapor flows out the outlet end opposite the fluid metering assembly through a pipe and enters a heat exchanger. The heat exchanger contains a heat absorptive medium which absorbs heat from the vaporized fluid to cause the fluid to condense and release its latent heat of vaporization to the heat absorptive medium. The condensed fluid flows to the heat storage tank and back to the supply tank for reuse. The recirculation is provided under pressure generated by the vaporized fluid entering the heat exchanger. The heat exchangers are modular and a plurality may be interconnected to provide a desired amount of heat storage capacity.
During operation of such a system, several conditions may result which detract from the operating efficiency of the system. Since the pressure of the vaporized fluid moves the condensed heat transfer fluid from the storage reservoir back to the fluid supply, conditions which dissipate the pressure tend to reduce the rate of return of the condensed heat transfer fluid back to the fluid supply. One such condition is the overall volume of the operating portions of the closed loop system. At times, a temporary reduction of the volume of the operating portions of the system is desired to lessen pressure dissipation in order to assure adequate return of condensed heat transfer fluid to the fluid supply tank.
Another condition which reduces the operating efficiency of the system occurs when extremely favorable sum conditions cause the linear vaporizer tube to heat up to a very high temperature. Concomitant with the very high temperature is a high pressure. The excessive heat conditions may cause the linear vaporizer tube to overheat or rupture.
Another condition which contributes to overall inefficiency is heat loss that results in the fluid supply tank. As hot fluid in the tank awaits being metered into the linear vaporizer tube, it tends to lose some of its heat to its surroundings.
Yet another condition which contributes to system inefficiency is the cooling and loss of heat from the heat transfer fluid to the outside surroundings of the system during conditions of low solar energy capture such as in the evening when the sun goes down or on cloudy days.
A thermoelectric generator system deriving its motive heat from solar energy, should make most efficient use of the solar energy which is collected and stored.
Therefore, it is an object of the invention to provide a closed loop solar energy collector system of improved operating efficiency having means to temporarily reduce the volume of the operating system in order to enhance ability of the pressure of the vaporized heat transfer fluid to move condensed heat transfer liquid back to the fluid supply.
Another object of the invention is to provide a means to quench the linear vaporizer tube when subject to excessively high operating temperatures and pressure.
Another object of the invention is to provide a fluid supply tank designed to reduce heat loss from the heat transfer fluid to the surroundings.
Another object of the invention is to provide a means for transferring a large portion of the heat transfer fluid away from the outside environment to portions of the system which are protected from the outside environment during low solar energy accumulating times such as after sundown or on cloudy days.
Another object of the invention is to provide a combined solar energy collecting and electric energy generating system which makes efficient use of the solar energy collected.
These and other objects are accomplished by the invention as described below.